The fluorinated polymers form a class of compounds having interesting properties for a great many applications, from paints to seals, optics, microelectronics, membrane technology and materials for energy applications (fuel cells, separators and electrolytes for lithium ion batteries, “backsheets” of photovoltaic panels). Among these fluorinated polymers, the copolymers are particularly interesting on account of their variety, morphology, exceptional properties and versatility.
Most copolymerization reactions employed in the prior art for preparing fluorinated copolymers (essentially fluorinated olefins having a double bond) are so-called conventional radical reactions.
Thus, the series of three articles grouped together under the title Radical Copolymerization of 2-Trifluoromethacrylic Monomers, by Ito et al., in Journal of Polymer Science A, 42: 1468-1527 (2004), deals with the formation of copolymers based on α-trifluoromethacrylic acid.
The document Radical Copolymerization of α-Trifluoromethacrylic Acid with Vinylidene Fluoride and Vinylidene Fluoride/Hexafluoropropene, by Souzy et al., in Macromol. Chem. Phys. 205: 476-485 (2004), describes a method of conventional copolymerization of vinylidene fluoride and α-trifluoromethacrylic acid.
However, techniques have also been proposed for controlled radical copolymerization, i.e. providing control of the molecular weight and of the polydispersity of the polymers, and the synthesis of copolymers with controlled architectures (block, grafted, alternating, gradient, hyperbranched, etc.). In particular, methods of radical copolymerization controlled by means of xanthate compounds have been described, under the name MADIX, for “Macromolecular Design via Interchange of Xanthates”.
The document Controlled Radical (co)polymerization of fluoromonomers, by B. Ameduri, in Macromolecules 43: 10163-10184 (2010), as well as the document From Vinylidene Fluoride (VDF) to the Applications of VDF-containing Polymers and Copolymers: Recent Developments and Future Trends, by B. Ameduri, in Chem. Rev. 109: 6632-6686 (2009), are two reviews summarizing relevant works in this field.
The document First Amphiphilic Poly(vinylidene fluoride-co-3,3,3-trifluoropropene)-b-oligo(vinyl alcohol)Block Copolymers as Potential Nonpersistent Fluorosurfactants from Radical Copolymerization Controlled by Xanthate, by Kostov et al., in Macromolecules 44: 1841-1855 (2011), describes the manufacture of fluorinated block copolymers based on a technique of the MADIX type.
The document Living/controlled free radical copolymerization of chlorotrifluoroethene and butyl vinyl ether under 60Co γ-ray irradiation in the presence of S-benzyl O-ethyl dithiocarbonate, by Liu et al., in Chem. Comm., 47: 7839-7841 (2011), provides another example of a method of copolymerization controlled by xanthate but considers copolymers based on CTFE and vinyl ethers exclusively.
The document Iodine Transfer Copolymerization of Vinylidene Fluoride and α-Trifluoromethacrylic Acid in Emulsion Process without Any Surfactants, by Boyer et al., in Journal of Polymer Science A, 47: 4710-4722 (2009), describes the synthesis of copolymers of vinylidene fluoride and α-trifluoromethacrylic acid using iodine compounds as chain transfer agents.
However, there is still a need to develop new fluorinated copolymers, in particular by means of methods of controlled radical copolymerization.